Excel Exception from HRESULT: 0x800AC472

Question

Excel Exception from HRESULT: 0x800AC472

I am exporting data to excel thru C# code.

while export is in progress, if I open any excel file (not necessariliy the one being created), I get the above error.

Earlier I was exporting on a background thread, but after reading various comments on google, I removed the background thread but the problem still exists.